Gas Of Choice Research Articles

Changing trends in suicides using helium or nitrogen – A 15-year study

A study was undertaken of autopsy cases of suicide where either helium or nitrogen gas had been used (taken from Forensic Science SA files, 2003–2017). 33 deaths involved helium (age range 19–94yrs, average 47yrs; M:F–2.7:1), compared to 23 cases of nitrogen inhalation (age range 29–93yrs, average 66yrs; M:F–2.3:1). The combined numbers of deaths due to both helium and nitrogen inhalation showed a steady increase (5: 2003–2007; 31: 2013–2017); however, while helium deaths plateaued (14: 2008–2012, 15: 2013–2017) nitrogen-related deaths increased 16-fold. Specifically, the percentage of cases due to nitrogen inhalation increased from 20 to 52%, compared to helium which fell from 80 to 48%. Continued observation of the study population is required with evaluation of other communities and larger populations to monitor this potential trend, and to determine whether nitrogen may be superseding helium as the gas of choice in plastic bag and other asphyxial suicides.

Efficient and Selectable Production of Reactive Species Using a Nanosecond Pulsed Discharge in Gas Bubbles in Liquid

A plasma gas bubble‐in‐liquid method for high production of selectable reactive species using a nanosecond pulse generator has been developed. The gas of choice is fed through a hollow needle in a point‐to‐plate bubble discharge, enabling improved selection of reactive species. The increased interface reactions, between the gas‐plasma and water through bubbles, give higher productivity. H2O2 was the predominant species produced using Ar plasma, while predominantly and NO2 were generated using air plasma, in good agreement with the observed emission spectra. This method has nearly 100% selectivity for H2O2, with seven times higher production, and 92% selectivity for , with nearly twice the production, compared with a plasma above the water.

Recent developments for an active UF6gas target for photon-induced fission experiments

Recent developments for an active uranium-hexafluoride-loaded gas target as well as results on the detector gas properties are presented. The gas of choice is a mixture of argon with small amounts of UF 6 . This contribution presents the experimental setup and focusses on the electron drift velocity with increasing UF 6 content. A time-dependent decrease in electron drift velocity is observed in our setup.

ESEM as a Tool for Studying High Temperature Electronics

Researchers studying materials and processes at high temperatures are often restricted to do evaluation afterwards and at room temperature using e.g. scanning electron microscopy (SEM). Limited by high vacuum, outgassing and non-conducting samples are difficult to study with SEM. For such samples, environmental scanning electron microscope (ESEM) is an alternative that is particularly suited also for high temperature in-situ studies. The electron detector in the ESEM make use of otherwise unwanted scattering of electrons as an amplifier of the signal, and by using differential pumping, it is possible to introduce several mbar of either oxygen, water vapor, or a gas of choice into the sample chamber while still maintaining the high-vacuum in the electron column. The auxiliary gas neutralizes surface charges built up by the electron beam, which makes it possible to image non-conductive and outgassing samples, thus making it possible to study e.g. polymeric and high temperature materials. Our ESEM, FEI XL30, have a heating stage making it possible to reach temperatures up to 1500°C. Equipped with electrical feed-throughs, the instrument can be used to study high temperature phenomena on electrically activated components. ESEM is an instrument that has found its use for biological and organic samples. However, less work has been done using it for high temperature processes. Here, we show real-time imaging of the sintering of dielectric and Ag thick-film prints on AlN substrates. The use of the electrical feed-throughs to activate electrical components and study them at high temperatures is also demonstrated. ESEM is a versatile tool for high temperature studies and in-situ analysis of electrical components, solder processes and different die-attach materials.